This invention relates to a piezoelectric laminate body. More particularly, this invention relates to a piezoelectric laminate body that is produced by laminating unit laminate bodies each comprising piezoelectric ceramic, or the like, and is suitable for a piezoelectric actuator for driving a fuel injection valve of an engine, a controlling valve of a mass flow controller, and so forth.
Piezoelectric devices have gained a wide application in various fields in recent years. When an electric field is applied to the piezoelectric device, a distortion proportional to the electric field develops in the piezoelectric device, generating thereby a strain (displacement). When a force is applied and the piezoelectric device is caused to undergo distortion, on the contrary, the electric properties of the piezoelectric device change in proportion to the displacement. Sheet-like piezoelectric devices having such properties are laminated to give a piezoelectric laminate body, which can be utilized as an actuator in various applications.
As described above, various displacements occur when the electric field is applied to the piezoelectric laminate body as described above. However, the quantity of displacement varies structurally depending on position, and cracks are therefore likely to occur in the piezoelectric laminate body. To prevent such cracks in the piezoelectric laminate body, various structures have been proposed in the past. A typical piezoelectric laminate body of this kind is described in, for example, Takahashi Sadayuki et al. xe2x80x9cMicro Piezoelectric Ceramic Actuatorxe2x80x9d, the transaction of the Society of Electronic Communication, pp. 55-59, May 17, 1983. The problems of the prior art technologies will be described later.
It is an object of the present invention to provide a piezoelectric laminate body that restricts to a minimum the difference in the quantity of displacement of a boundary between an electrode center portion of a unit laminate body and alternate electrode portions upon the application of an electric field, by improving a laminate structure of a piezoelectric laminate body.
According to the first aspect of the present invention, there is provided a piezoelectric laminate body produced by serially laminating a plurality of alternate electrode structure type laminate bodies each including a center electrode portion as a driving portion and alternate electrode portions as non-driving portions disposed on both sides of the center electrode portion, wherein the unit laminate body on the upper side, among a plurality of unit laminate bodies, is disposed at the both-side alternate electrode portions thereof in the spaced-apart relation with the both-side alternate electrode portions of the unit laminate body just below the upper unit laminate body.
According to the second aspect of the present invention, there is provided a piezoelectric laminate body produced by serially laminating a plurality of unit laminate bodies, wherein each of the unit laminate bodies is constituted as an alternate, electrode structure type unit laminate body including a center electrode portion as a driving unit and alternate electrode portions as non-driving portions disposed on both sides of the center electrode portion; and the unit laminate body on the upper side, among a plurality of unit laminate bodies, is serially laminated at the center electrode portion thereof in such a fashion that it is deviated, at both-side alternate electrode portions thereof, by a predetermined angle with respect to both-side alternate electrode portions of both-side alternate electrode portions of the unit laminate body just below the upper unit laminate body in a laminating direction while it is separated from both-side alternate electrode portions of the lower unit laminate body.
According to the third aspect of the present invention, there is provided a piezoelectric laminate body produced by serially laminating a plurality of unit laminate bodies, wherein each of the unit laminate bodies is constituted as an alternate electrode structure type unit laminate body having a center electrode portion as a driving portion and alternate electrode portions as non-driving portions, disposed on the outer peripheral side of the center electrode portion; and each of a plurality of unit laminate bodies on the upper side is laminated in such a fashion as to deviate at the alternate electrode portion thereof from the alternate electrode portion of the unit laminate body just below the upper unit laminate body in a laminating direction.
According to the fourth aspect of the present invention, there is provided a piezoelectric laminate body produced by serially and alternately laminating unit laminate bodies and inter-connection laminate bodies, wherein each of the unit laminate bodies includes alternate electrode portions as non-driving portions on an outer peripheral side of a center electrode portion, as a driving portion, and constituted, with the inter-connection laminate body adjacent thereto, as an alternate electrode structure type unit laminate body, and the unit laminate body on the upper side and the adjacent inter-connection laminate body thereof are laminated in such a fashion as to separate and deviate at the alternate electrode portion thereof from the alternate electrode portion of the unit laminate body and the adjacent inter-connection laminate body just below the upper unit laminate body in a laminating direction.